Metal Spinning - Velocity Stacks

Does anyone here have experience/recommendations of a UK-based company who can metal-spin small runs of custom velocity stacks?

I am in the throes of an exact replica of Jaguar's XJ13 (as it was in 1966 and not as it is today after its crash/rebuild in 1972/73). I am now turning my thoughts to the inlet manifolding/butterflies/stacks and wondered if any of you could please point me in the direction of a UK-based company who can do a small run of velocity stacks. I do have detailed dimensions of what I am looking for and hope to end up with something like the following. Before any of you point out - yes, I know it isn't an ideal shape but this was 1966 and I need to exactly replicate it as it was - warts and all!

I have dealt with these guys http://www.metalspin...r-location.html . They make all sorts of things, up to and including motorbike wheels. 6mm stainless was their maximum, and 0.7 mm aluminium was the thinnest. Very cluey, and cheap and fast.

Does anyone here have experience/recommendations of a UK-based company who can metal-spin small runs of custom velocity stacks?

I am in the throes of an exact replica of Jaguar's XJ13 (as it was in 1966 and not as it is today after its crash/rebuild in 1972/73). I am now turning my thoughts to the inlet manifolding/butterflies/stacks and wondered if any of you could please point me in the direction of a UK-based company who can do a small run of velocity stacks. I do have detailed dimensions of what I am looking for and hope to end up with something like the following. Before any of you point out - yes, I know it isn't an ideal shape but this was 1966 and I need to exactly replicate it as it was - warts and all!

Engine originally installed in XJ13

Detail

Nev - Very nice photos - is that a single cam on each cylinder bank? I thought it was a twincam engine? Looks like a standard XK cam cover?

Now THAT engine is a serious challenge to a chassis designer. None of your sub 100kg F1 motors but a nice bit lump with a high CG and probably 300kg+.

Looking at the photo and my recollection of a lovely cutaway of the XJ13 I think the designers were smart enouigh to fix the rear radius arms onto the engine so the braking loads etc are reacted directly into the suspension

Thanks for the replies gentlemen - I will check out your suggested links.

Yes, it is DOHC and yes, the rear suspension hangs off the block. The driveshaft from the transaxle (ZF) forms an upper link and there is a triangulated pressed-steel lower link. There are two trailing arms on each side which connect the wheels to the mount you can see in the photo. The mount is connected to both the block and the sump.

I do have a number of original documents containing pages and pages of manual calculations. These are the days before computers don't forget! When I can make some time I plan to summarise them (assuming I can make sense of them ) and add to my personal blog (cos I'm sad like that ....). Here is a previously unknown original photograph showing how the engine mount (steel) was originally built up in 1965:

I see now that it is a DOHC. Why would they go to all the trouble of putting the intakes here rather than in the "vee"? I did see somewhere that they were XK heads.

Hi - the heads are similar in basic design to the XK heads (hemispherical combustion chambers etc) but differ dimensionally. Here is an extract from my blog post (Prototype V12 Stripdown)

The V12 cylinder head design is very similar to the 6-cylinder XK engine in basics such as valve operation with a few significant differences. In an attempt to arrive at a more compact and efficient combustion chamber, the chamber depth was reduced to 1.03" (from the XK's 1.30") and the included valve angle was reduced. .... the V12 prototype engine has equal firing impulses along each bank and can be carburetted as an in-line 6 cylinder. The bore and stroke is 87mm x 70mm giving a displacement of 4991cc.

All prototype engines were fitted with twin 6-cylinder distributors. One of the many changes made when Jaguar rebuilt the XJ13 after its crash in 1971 was their replacement by a single 12-cylinder distributor (a design carried forward to the production SOHC engine). One of the two distributors, the "master", contained two sets of contact-breakers plus a centrifugal advance mechanism that served both distributors. The second distributor, the "slave", was simply a distributor for the H.T. current. As well as the distributor(s), space was needed in the "V" for the lucas mechanical fuel injection metering unit. Perhaps this is one reason why they chose to make best use of space and used the gap between the cams for the inlets. It does make it a nightmare to access the spark plugs though

Hi - the heads are similar in basic design to the XK heads (hemispherical combustion chambers etc) but differ dimensionally. Here is an extract from my blog post (Prototype V12 Stripdown)

The V12 cylinder head design is very similar to the 6-cylinder XK engine in basics such as valve operation with a few significant differences. In an attempt to arrive at a more compact and efficient combustion chamber, the chamber depth was reduced to 1.03" (from the XK's 1.30") and the included valve angle was reduced. .... the V12 prototype engine has equal firing impulses along each bank and can be carburetted as an in-line 6 cylinder. The bore and stroke is 87mm x 70mm giving a displacement of 4991cc.

All prototype engines were fitted with twin 6-cylinder distributors. One of the many changes made when Jaguar rebuilt the XJ13 after its crash in 1971 was their replacement by a single 12-cylinder distributor (a design carried forward to the production SOHC engine). One of the two distributors, the "master", contained two sets of contact-breakers plus a centrifugal advance mechanism that served both distributors. The second distributor, the "slave", was simply a distributor for the H.T. current. As well as the distributor(s), space was needed in the "V" for the lucas mechanical fuel injection metering unit. Perhaps this is one reason why they chose to make best use of space and used the gap between the cams for the inlets. It does make it a nightmare to access the spark plugs though

Didnt the velocity stacks include a built in fuel feed venturi?
I am not sure but I think this is so on Lucas fuel injection.
Was it a slide plate on each pair of stacks or butterflys?
I can also remember seeing the car with carbs at one time, at least I think so.

The low cam covers in the engine v make it look like it has only two cams when it has four.

Didnt the velocity stacks include a built in fuel feed venturi?I am not sure but I think this is so on Lucas fuel injection.Was it a slide plate on each pair of stacks or butterflys?I can also remember seeing the car with carbs at one time, at least I think so.

The low cam covers in the engine v make it look like it has only two cams when it has four.

Hi - yes, there is a type of venturi and they have butterflies. I will have to fabricate something similar. Suitable throttle-bodies aren't readily available so I will have to make the butterflies too. I was thinking along the fundamental design used by Weber in their downdraft carbs. Here is a photo looking down a XJ13 trumpet:

The only quad-cam prototype engine fitted with carbs (a sextuplet of 2 1/2" SUs) was my engine. It was tested in two Mk10 Jaguars and, although it retained the Lucas FI in the first Mk10, it had SUs installed by the time it was fitted to the second Mk10. Here is a picture of my engine in period (taken in the early 1970s when Jaguar displayed the engine in Coventry before it was shipped out to Germany). Everything except for the inlet manifolding/carbs has survived intact. I often wonder if the triple carb manifolds survived?

Hi - yes, there is a type of venturi and they have butterflies. I will have to fabricate something similar. Suitable throttle-bodies aren't readily available so I will have to make the butterflies too. I was thinking along the fundamental design used by Weber in their downdraft carbs. Here is a photo looking down a XJ13 trumpet:

The only quad-cam prototype engine fitted with carbs (a sextuplet of 2 1/2" SUs) was my engine. It was tested in two Mk10 Jaguars and, although it retained the Lucas FI in the first Mk10, it had SUs installed by the time it was fitted to the second Mk10. Here is a picture of my engine in period (taken in the early 1970s when Jaguar displayed the engine in Coventry before it was shipped out to Germany). Everything except for the inlet manifolding/carbs has survived intact. I often wonder if the triple carb manifolds survived?

Now that's what I call a proper engine. You can see why the intakes weren't in the vee.

Hi - yes, there is a type of venturi and they have butterflies. I will have to fabricate something similar. Suitable throttle-bodies aren't readily available so I will have to make the butterflies too. I was thinking along the fundamental design used by Weber in their downdraft carbs. Here is a photo looking down a XJ13 trumpet:

The only quad-cam prototype engine fitted with carbs (a sextuplet of 2 1/2" SUs) was my engine. It was tested in two Mk10 Jaguars and, although it retained the Lucas FI in the first Mk10, it had SUs installed by the time it was fitted to the second Mk10. Here is a picture of my engine in period (taken in the early 1970s when Jaguar displayed the engine in Coventry before it was shipped out to Germany). Everything except for the inlet manifolding/carbs has survived intact. I often wonder if the triple carb manifolds survived?

I used to rebuild and tune weber carbs. knife edge butterflys etc.We have two old v8 maseratis with engines being rebuilt here and I will be setting up the quad weber downdrafts for these soon.Might be able to help you.The throttle bodies may be similar or an adaptation of something weber.

I used to rebuild and tune weber carbs. knife edge butterflys etc.We have two old v8 maseratis with engines being rebuilt here and I will be setting up the quad weber downdrafts for these soon.Might be able to help you.The throttle bodies may be similar or an adaptation of something weber.

Yes - I was thinking that Jaguar won't have had the throttle-bodies specially made and may have modified something. That would explain why the trumpets are so close together (to suit the dual throttle-bodies). Given a free hand, they would have probably had separate throttle bodies and straightened the inlets (as they did for the rebuild in 1972/73 after the car was crashed). However, I want my recreation to be as the car was in 1966. The question is, what did they use/modify? The trumpets themselves and the sections from the head to the throttle bodies should be quite easy to make to suit.

The following picture shows the part we are talking about (coloured yellow). Would you be able to come up with something suitable? Anyone else know of something similar?

The following picture shows the part we are talking about (coloured yellow). Would you be able to come up with something suitable? Anyone else know of something similar?

Hilborn made close-coupled 2-throat throttle bodies like that for sprint cars... Chevy small block intakes are spaced that way... and early Hilborn unts bolted four TBs to a "valley plate". Later versions cast the valley plate and all 8 throttles as one piece. There were a lot of versions, but I'm not sure any were that short in height. Give your freind the retired pattern maker some dimensions and a case of beer. If you don't have a freind who is a retired pattern maker, maybe it's time to find a new friend.

I was thinking more along the lines of Jaguar casting their own throttle bodies and using available butterflys and spindles.
Probably Weber parts.
I see no problem with casting the actual bodies, or machining them.
It is also fairly easy to machine turn the velocity stacks although I see join welds near the base flanges.
I see the difficult part as casting and finishing the internal venturi/fuel nozzles.

I have discused it with one of our guys who runs the machine shop and I think we could sort most of it out for you.

What details and parts have you for the rest of the injection system?
Have you any detailed drawings or dimensions/specs.
The sizes for the internal venturi/fuel nozzles is critical as is the fuel pressure etc.
Sorting historic injection systems and ignition systems becomes more difficult the greater the number of cylinders.
To balance it up will require a lot of fettling work.

Gentlemen - a quick "thank-you" to all who helped give me enough confidence to produce these items myself. Here is where I am so far ....

I started with original drawings/dimensions of the inlets as fitted to my head 1966/67 and used these as a starting point. I am lucky enough to have ended up with the only two examples of the ultimate development of the prototype quad-cam racing heads.

I started by making the short inlets to mount my chosen single throttle bodies on the heads. I decided to make these from three pieces - two flanges and a distance piece rather than casting them as Jaguar did. However, I can always cast some once I have finalised the layout etc.

Machining the offset 33mm hole at the head to run up at 41 degrees and end up with a 42mm hole exactly centred presented me with a bit of a challenge but I succeeded in the end!

I spent quite a lot of time matching each distance piece to its own port before polishing.

While I was doing this my velocity stacks were being spun in steel to the required dimensions.

I used Jenvey 42mm single throttle-bodies which happened to almost exactly match the required dimensions both for height and ID. I elected to aim for straight-through inlets rather than angle the inlets towards each other as Jaguar did in their first attempts in the XJ13. I felt justified in doing this as they later adopted this configuration when they built their one-and-only full race engine (which was never installed in the XJ13 but which supplied the heads for my engine). In this configuration they achieved the highest bhp figures for this engine.

My next task is to sort out a suitable injection point. At present I am thinking along the lines of an off-the-shelf Kinsler nozzle body installed using a modified Weber auxiliary venturi.

Kinsler can also supply valves/vapour-separator/pipework etc to complete the FI installation. I then need to sort out linkages. That will only get me to the start point of course as I will then have the task of optimising the fuel cam etc when the engine is running on the dyno.

I thank you again for your help so far and would appreciate any observations/comments while I am at this very early stage in the FI setup.

I don't think you ever forget the first time you see metal spinning. The first time I saw it was - er - oh yes, Model Engineering Exhibition, when I were a lad, saw a disc of bass turned into a useful household container in hardly any time.

I don't think you ever forget the first time you see metal spinning. The first time I saw it was - er - oh yes, Model Engineering Exhibition, when I were a lad, saw a disc of bass turned into a useful household container in hardly any time.

Yes I agree Tony - it is mesmeric! If anyone wants to see a selection of videos just search for "metal spinning" on You Tube. There's one here Metal Spinning. Its not the company that spun mine - just an example. Before the end of the video I found myself counting his fingers ...

It's heartening to see that so many Health and Safety recommendations have been eagerly taken up by the Metal Spinning Industry - no loose clothing, gloves, goggles, ear defenders, mask, absolutely no slowing of the workpiece by placing a hand on it. We can all learn so much from this educational video.

My comment was not specific to metal's ductility, more the applications it sees.

I have just been drawing up some designs of some pretty solid mechanical bits that weigh 6 tons then see some small sheet being shaped, the diversity is amazing - as the boss of Ford basically said recently in response to a "future car materials question"; "Show me any material that can do all that steel can and I'll call you a liar!".

My comment was not specific to metal's ductility, more the applications it sees.

I have just been drawing up some designs of some pretty solid mechanical bits that weigh 6 tons then see some small sheet being shaped, the diversity is amazing - as the boss of Ford basically said recently in response to a "future car materials question"; "Show me any material that can do all that steel can and I'll call you a liar!".